Support of Network Observation Timestamping in YANG Notifications

To correlate network data among different Network Telemetry planes as described in Section 3.1 of or among different YANG push subscription types defined in Section 3.1 of , network observation timestamping describes when the state change was observed or from when to when the data was accounted. This is essential for understanding the timely relationship among these different planes and YANG push subscription types. With the delay between the YANG Notification export and the arrival at the downstream system storing the data can be measured. With network observation timestamping described in this document, the delay between the network observation and the data export of the YANG push publisher process can be measured as well, extending the delay measurement scope from the time the network observation and storing the data. When the time bucket length in a time series database and the periodical YANG push subscription time is identical, the eventTime of the netconf notification message header is used for indexing, there is variable delay between the observation time and the eventTime, and the anchor-time as described in Section 4.2 of is close to the time bucket boundaries, a time bucket is going to have periodically 0 or 2 measurements indexed instead of 1. Leading to inconsistent accounting errors in the time series database. This problem is resolved by using the observation-time instead of the eventTime for time series database indexing. By extending the YANG Notification header with the YANG objects observation-time for periodical and state-changed-observation-time for on-change subscriptions these use cases can be addressed accordingly.

The following terms are defined in and are not redefined here: Publisher Receiver Subscription In addition, this document defines the following terms: Observation-time: Describes the measurement observation time for the "push-update" notification in a "periodical" subscription. State-changed-observation-time: Describes the time when the network state change was observed.

Besides the Subscription ID as described in Section 3.7 of , the following network observation time metadata objects are part of "push-update" and "push-change-update" notifications.

observation-time:: Describes the measurement observation time for the "push-update" notification in a "periodical" subscription. By comparing the "observation-time" of two "push-update" notifications, the collector can deduce the actual cadence of the measurements, and compare it with the configured one.
state-changed-observation-time:: Describes in the "push-change-update" notification in a "on-change" subscription the time when the network state change was observed after the subscription was initially established. In case of an "on-change sync on start" subscription it describes the time when the network state change was observed before the subscription was established.

provides an example of a JSON encoded, , "push-change-update" notification message over HTTPS-based or UDP-based transport for the same subscription.

This YANG module augments the "ietf-yang-push" module with the observation-time in the "push-update" and "push-change-update" streaming update notifications.

The following is the YANG tree diagram for the ietf-yang-push-netobs-timestamping YANG module

The following is the YANG tree diagram for the ietf-yang-push-netobs-timestamping augmentation within the ietf-subscribed-notifications, including the RPCs and notifications.

| {sn:subtree}? +--:(datastore-xpath-filter) +-- datastore-xpath-filter? yang:xpath1.0 {sn:xpath}? augment /sn:modify-subscription/sn:input: +---w (update-trigger)? +--:(periodic) | +---w periodic! | +---w period centiseconds | +---w anchor-time? yang:date-and-time +--:(on-change) {on-change}? +---w on-change! +---w dampening-period? centiseconds augment /sn:modify-subscription/sn:input/sn:target: +--:(datastore) +-- datastore identityref +-- (selection-filter)? +--:(by-reference) | +-- selection-filter-ref | selection-filter-ref +--:(within-subscription) +-- (filter-spec)? +--:(datastore-subtree-filter) | +-- datastore-subtree-filter? | {sn:subtree}? +--:(datastore-xpath-filter) +-- datastore-xpath-filter? yang:xpath1.0 {sn:xpath}? augment /sn:subscription-started: +--ro (update-trigger)? +--:(periodic) | +--ro periodic! | +--ro period centiseconds | +--ro anchor-time? yang:date-and-time +--:(on-change) {on-change}? +--ro on-change! +--ro dampening-period? centiseconds +--ro sync-on-start? boolean +--ro excluded-change* change-type augment /sn:subscription-started/sn:target: +--:(datastore) +-- datastore identityref +-- (selection-filter)? +--:(by-reference) | +-- selection-filter-ref | selection-filter-ref +--:(within-subscription) +-- (filter-spec)? +--:(datastore-subtree-filter) | +-- datastore-subtree-filter? | {sn:subtree}? +--:(datastore-xpath-filter) +-- datastore-xpath-filter? yang:xpath1.0 {sn:xpath}? augment /sn:subscription-modified: +--ro (update-trigger)? +--:(periodic) | +--ro periodic! | +--ro period centiseconds | +--ro anchor-time? yang:date-and-time +--:(on-change) {on-change}? +--ro on-change! +--ro dampening-period? centiseconds +--ro sync-on-start? boolean +--ro excluded-change* change-type augment /sn:subscription-modified/sn:target: +--:(datastore) +-- datastore identityref +-- (selection-filter)? +--:(by-reference) | +-- selection-filter-ref | selection-filter-ref +--:(within-subscription) +-- (filter-spec)? +--:(datastore-subtree-filter) | +-- datastore-subtree-filter? | {sn:subtree}? +--:(datastore-xpath-filter) +-- datastore-xpath-filter? yang:xpath1.0 {sn:xpath}? augment /sn:filters: +--rw selection-filter* [filter-id] +--rw filter-id string +--rw (filter-spec)? +--:(datastore-subtree-filter) | +--rw datastore-subtree-filter? | {sn:subtree}? +--:(datastore-xpath-filter) +--rw datastore-xpath-filter? yang:xpath1.0 {sn:xpath}? augment /sn:subscriptions/sn:subscription: +--rw (update-trigger)? +--:(periodic) | +--rw periodic! | +--rw period centiseconds | +--rw anchor-time? yang:date-and-time +--:(on-change) {on-change}? +--rw on-change! +--rw dampening-period? centiseconds +--rw sync-on-start? boolean +--rw excluded-change* change-type augment /sn:subscriptions/sn:subscription/sn:target: +--:(datastore) +--rw datastore identityref +--rw (selection-filter)? +--:(by-reference) | +--rw selection-filter-ref | selection-filter-ref +--:(within-subscription) +--rw (filter-spec)? +--:(datastore-subtree-filter) | +--rw datastore-subtree-filter? | {sn:subtree}? +--:(datastore-xpath-filter) +--rw datastore-xpath-filter? yang:xpath1.0 {sn:xpath}? rpcs: +---x resync-subscription {on-change}? +---w input +---w id sn:subscription-id notifications: +---n push-update | +--ro id? sn:subscription-id | +--ro datastore-contents? | +--ro incomplete-update? empty | +--ro ypnt:observation-time? yang:date-and-time +---n push-change-update {on-change}? +--ro id? | sn:subscription-id +--ro datastore-changes | +--ro yang-patch | +--ro patch-id string | +--ro comment? string | +--ro edit* [edit-id] | +--ro edit-id string | +--ro operation enumeration | +--ro target target-resource-offset | +--ro point? target-resource-offset | +--ro where? enumeration | +--ro value? +--ro incomplete-update? empty +--ro ypnt:state-changed-observation-time? yang:date-and-time ]]>

The YANG module has one leave augmenting the model of Subscription to YANG Notifications.

file "ietf-yang-push-netobs-timestamping@2023-03-06.yang" module ietf-yang-push-netobs-timestamping { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-push-netobs-timestamping"; prefix ypnt; import ietf-yang-types { prefix yang; reference "RFC 6991: Common YANG Data Types"; } import ietf-yang-push { prefix yp; reference "RFC 8641: Subscription to YANG Notifications for Datastore Updates"; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: Authors: Thomas Graf Benoit Claise Alex Huang Feng "; description "Defines YANG push event notification header with the observation time in push-update and push-change-update notifications. Copyright (c) 2023 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; revision 2023-03-06 { description "First revision"; reference "RFC XXXX: Support of YANG Notifications Observation Time"; } feature yang-push-change-update-obs-timestamp { description "This feature indicates the YANG-push Notifications support the observation timestamps in the push-change-update notifications."; } feature yang-push-update-obs-timestamp { description "This feature indicates the YANG-push Notifications support the observation timestamps in the push-update notifications."; } grouping yang-push-update-obs-timestamp { description "This grouping adds the start timestamp and the end timestamp of the observed metrics."; leaf observation-time { type yang:date-and-time; description "This is the time when metrics started counting."; } } grouping yang-push-change-update-obs-timestamp { description "This grouping adds the timestamp of the recorded event."; leaf state-changed-observation-time { type yang:date-and-time; description "This is the time when event happened."; } } // Event notifications augment "/yp:push-update" { description "This augmentation adds the start timestamp of the counted metrics in the push-update notification."; uses ypnt:yang-push-update-obs-timestamp; } augment "/yp:push-change-update" { description "This augmentation adds the timestamp of the event in the push-change-update notification."; uses ypnt:yang-push-change-update-obs-timestamp; } } ]]>



    
      Note to the RFC-Editor: Please remove this section before
      publishing.

      
        6WIND implemented this document for a YANG Push publisher on UDP-based Transport for Configured
        Subscriptions in their VSR platform.
      
    

    
      The security considerations for the YANG notifications subscription
      mechanism are described in . This document adds
      no additional security considerations.
    

    
      This document describes the URI used for the IETF XML Registry and
      registers a new YANG module name.

      
        IANA is requested to add this document as a reference in the
        following URI in the IETF XML Registry .

        
          URI:

          urn:ietf:params:xml:ns:yang:ietf-yang-push-netobs-timestamping

          Registrant Contact:

          The IESG.

          XML:

          N/A; the requested URI is an XML namespace.

          Reference:

          RFC5277; RFC-to-be
        
      

      
        This document registers the following YANG module in the YANG
        Module Names Registry , within the "YANG
        Parameters" registry:

        
          name:

          ietf-yang-push-netobs-timestamping

          namespace:

          urn:ietf:params:xml:ns:yang:ietf-yang-push-netobs-timestamping

          prefix:

          ypnt

          Reference:

          RFC-to-be
        
      
    

    
      
        For "on-change sync on start" subscriptions, if the timestamp for
        the network state change was observed before the subscription was
        established and is not recorded in the YANG datastore, then no
        timestamp should be populated to state-changed-observation-time.
      
    

    
      The authors would like to thank Rob Wilton, Nick Corran, Pierre
      Francois Ahmed Elhassany and Jean Quilbeuf for their review and valuable
      comments.